Sealing device

ABSTRACT

Provided is a sealing device that is capable of exhibiting a sealing function even in a condition in which a fluid pressure is low while suppressing its sliding torque. A sealing device  100  is characterized by including: a seal ring  200  made of resin which is in close contact with a side wall surface on a low pressure side of an annular groove  410 , and slides against an inner peripheral surface of a shaft hole in a housing  500  through which a shaft  400  is inserted; and a metal spring  300  which is provided along an inner peripheral surface of the seal ring  200  in a state in which a gap is formed between the metal spring  300  and a groove bottom surface of the annular groove  410 , and presses the seal ring  200  toward an outer peripheral surface side, wherein a concave portion  220  is formed on an outer peripheral surface of the seal ring  200  which extends from an end portion on a high pressure side of the outer peripheral surface to a position which does not reach an end portion on a low pressure side of the outer peripheral surface, and introduces a fluid from the high pressure side.

TECHNICAL FIELD

The present invention relates to a sealing device which seals an annulargap between a shaft and a shaft hole of a housing.

BACKGROUND ART

In an automatic transmission (AT) and a continuously variabletransmission (CVT) for automobiles, in order to hold a hydraulicpressure, a seal ring which seals an annular gap between a shaft and ahousing which rotate relative to each other is provided. With referenceto FIGS. 33 and 34, a seal ring according to a conventional art will bedescribed. FIG. 33 is a schematic cross-sectional view showing a sealring according to the conventional art in a condition in which thehydraulic pressure is not held. FIG. 34 is a schematic cross-sectionalview showing the seal ring according to the conventional art in acondition in which the hydraulic pressure is held. In the case of a sealring 600 according to the conventional art, the seal ring 600 isconfigured so as to seal an annular gap between a shaft 400 and a shafthole of a housing 500 by being attached to an annular groove 410provided on an outer periphery of the shaft 400, and being slidably incontact with an inner peripheral surface of the shaft hole of thehousing 500, through which the shaft 400 is inserted, and a side wallsurface of the annular groove 410.

In the seal ring 600 which is used for the above described purpose, itis required to sufficiently reduce a sliding torque. Accordingly, thecircumference of an outer peripheral surface of the seal ring 600 isconfigured to be shorter than the circumference of the inner peripheralsurface of the shaft hole of the housing 500, thus it is configured tohave no interference. Consequently, in a condition in which an engine ofan automobile is operated and the hydraulic pressure is high, the sealring 600 is expanded in diameter by the hydraulic pressure and makesclose contact with the inner peripheral surface of the shaft hole andthe side wall surface of the annular groove 410 to thereby exhibit afunction of sufficiently holding the hydraulic pressure (see FIG. 34).In contrast to this, in a condition in which the hydraulic pressure isnot applied due to stoppage of the engine, the seal ring 600 isconfigured so as to be apart from the inner peripheral surface of theshaft hole and the side wall surface of the annular groove 410 (see FIG.33).

However, in the case of the seal ring 600 which is configured in theabove described manner, the seal ring 600 does not exhibit a sealingfunction in the condition in which the hydraulic pressure is notapplied. Accordingly, in a configuration such as AT or CVT, in whichgear shifting control is performed by oil which is pressure-fed by ahydraulic pump, when it is in a no-load condition in which the hydraulicpump is stopped (e.g., during an idling stop), the oil sealed by theseal ring 600 may no longer be sealed and return to an oil pan, therebyleaving no oil in the vicinity of the seal ring 600. Consequently, whenthe engine is started (re-started) from such a condition, the operationis started in a condition in which no oil is present in the vicinity ofthe seal ring 600; hence, without lubrication, a problem arises in thatresponsiveness or operativity may be poor.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Patent No. 4665046. Patent Literature 2:Japanese Patent Application Laid-open No. 2011-144847. Patent Literature3: Japanese Patent Application Laid-open No. 2010-265937

SUMMARY OF INVENTION Technical Problem

An object of the present invention is to provide a sealing device thatis capable of exhibiting a sealing function even in a condition in whicha fluid pressure is low while suppressing its sliding torque.

Solution to Problem

In order to solve the above problem, the present invention has adoptedthe following means.

That is, the sealing device according to the present invention is asealing device which is attached to an annular groove provided on anouter periphery of a shaft and holds a fluid pressure in a sealingtarget area by sealing an annular gap between the shaft and a housingrotating relative to each other, the sealing target area beingconfigured such that the fluid pressure changes, the sealing deviceincluding: a seal ring made of resin which is in close contact with aside wall surface on a low pressure side of the annular groove, andslides against an inner peripheral surface of a shaft hole in thehousing through which the shaft is inserted; and a metal spring which isprovided along an inner peripheral surface of the seal ring in a statein which a gap is formed between the metal spring and a groove bottomsurface of the annular groove, and presses the seal ring toward an outerperipheral surface side, wherein a concave portion is formed on an outerperipheral surface of the seal ring which extends from an end portion ona high pressure side of the outer peripheral surface to a position whichdoes not reach an end portion on a low pressure side of the outerperipheral surface, and introduces a fluid from the high pressure side.

Note that, in the present invention, the “high pressure side” denotesone side where a pressure is high when a pressure difference is createdbetween two sides of the sealing device, and the “low pressure side”denotes another side where the pressure is low when the pressuredifference is created between the two sides of the sealing device.

According to the sealing device of the present invention, the seal ringis pressed towards the outer peripheral surface side by the metalspring. Accordingly, even in a condition in which the fluid pressure isnot applied (the pressure difference is not created) or the fluidpressure is almost not applied (the pressure difference is almost notcreated), the seal ring is contact with the inner peripheral surface ofthe shaft hole of the housing, thereby exhibiting a sealing function.Consequently, it is possible to hold the fluid pressure from immediatelyafter the start of increase of the fluid pressure in the sealing targetarea. In addition, the concave portion is formed on the outer peripheralsurface of the seal ring, and the fluid is introduced into the concaveportion from the high pressure side. Accordingly, even when the fluidpressure is increased, the fluid pressure acts towards the innerperipheral surface side within an area where the concave portion isprovided. Consequently, it is possible to prevent the increase ofpressure acting towards the outer peripheral surface side via the sealring due to the increase of the fluid pressure, thereby making itpossible to suppress a sliding torque.

Since the metal spring is provided so as to be placed along the innerperipheral surface of the seal ring in the state in which the gap isformed between the metal spring and the groove bottom surface of theannular groove, the metal spring is hardly influenced by eccentricity ofthe shaft and the housing. In addition, the seal ring and the metalspring would not rotate relative to each other. Consequently, the sealring and the metal spring would not slide relative to each other; hencethe inner peripheral surface side of the seal ring would not be abradeddue to sliding.

In addition, a plurality of the concave portions may preferably beformed at intervals in a circumferential direction.

When such a configuration is adopted, a portion between the two concaveportions maintains a state in which it is in contact with the innerperipheral surface of the shaft hole of the housing, and it becomespossible to suppress degrading of the rigidity of the seal ring.Consequently, it becomes possible to prevent the seal ring from beingtilted within the annular groove, and stabilize an attachment state ofthe seal ring.

Further, a guide portion which positions the metal spring in an axialdirection (a direction of a central axis of the shaft; the same shallapply hereinafter) may preferably be formed on the inner peripheralsurface of the seal ring.

Accordingly, it becomes possible to prevent the metal spring from beingdisplaced in the axial direction. Consequently, the seal ring can bepressed towards the outer peripheral surface side stably by the metalspring.

In addition, another sealing device of the present invention is asealing device which is attached to an annular groove provided on anouter periphery of a shaft and holds a fluid pressure in a sealingtarget area by sealing an annular gap between the shaft and a housingrotating relative to each other, the sealing target area beingconfigured such that the fluid pressure changes, the sealing deviceincluding: a seal ring made of resin which is in close contact with aside wall surface on a low pressure side of the annular groove, andslides against an inner peripheral surface of a shaft hole in thehousing through which the shaft is inserted; and a metal spring which isprovided along an inner peripheral surface of the seal ring in a statein which a gap is formed between the metal spring and a groove bottomsurface of the annular groove, and presses the seal ring toward an outerperipheral surface side, wherein a concave portion is formed on an outerperipheral surface of the seal ring which extends from an end portion ona high pressure side of the outer peripheral surface to a position whichdoes not reach an end portion on a low pressure side of the outerperipheral surface, and introduces a fluid from the high pressure side,and a guide portion which positions the metal spring in an axialdirection is formed on the inner peripheral surface of the seal ring,and a protrusion which prevents the metal spring from being detached toan inner peripheral surface side is provided at a tip of the guideportion.

Still further, yet another sealing device of the present invention is asealing device which is attached to an annular groove provided on anouter periphery of a shaft and holds a fluid pressure in a sealingtarget area by sealing an annular gap between the shaft and a housingrotating relative to each other, the sealing target area beingconfigured such that the fluid pressure changes, the sealing deviceincluding: a seal ring made of resin which is in close contact with aside wall surface on a low pressure side of the annular groove, andslides against an inner peripheral surface of a shaft hole in thehousing through which the shaft is inserted; and a metal spring which isprovided along an inner peripheral surface of the seal ring in a statein which a gap is formed between the metal spring and a groove bottomsurface of the annular groove, and presses the seal ring toward an outerperipheral surface side, wherein a concave portion is formed on an outerperipheral surface of the seal ring which extends from an end portion ona high pressure side of the outer peripheral surface to a position whichdoes not reach an end portion on a low pressure side of the outerperipheral surface, and introduces a fluid from the high pressure side,and an abutment portion is provided at one position on the seal ring ina circumferential direction, and protrusions which restrict a movementof the metal spring in the circumferential direction are provided on theinner peripheral surface on both sides of the abutment portion.

Still further, yet another sealing device of the present invention is asealing device which is attached to an annular groove provided on anouter periphery of a shaft and holds a fluid pressure in a sealingtarget area by sealing an annular gap between the shaft and a housingrotating relative to each other, the sealing target area beingconfigured such that the fluid pressure changes, the sealing deviceincluding: a seal ring made of resin which is in close contact with aside wall surface on a low pressure side of the annular groove, andslides against an inner peripheral surface of a shaft hole in thehousing through which the shaft is inserted; and a metal spring which isprovided along an inner peripheral surface of the seal ring in a statein which a gap is formed between the metal spring and a groove bottomsurface of the annular groove, and presses the seal ring toward an outerperipheral surface side, wherein a concave portion is formed on theinner peripheral surface of the seal ring which extends from an endportion on a high pressure side of the outer peripheral surface to aposition which does not reach an end portion on a low pressure side ofthe outer peripheral surface, and introduces a fluid from the highpressure side, a guide portion which positions the metal spring in anaxial direction, and a first protrusion which prevents the metal springfrom being detached to an inner peripheral surface side is provided at atip of the guide portion, and an abutment portion is provided at oneposition on the seal ring in a circumferential direction, and secondprotrusions which restrict a movement of the metal spring in thecircumferential direction are provided on the inner peripheral surfaceon both sides of the abutment portion.

In addition, in each of the aspects of the invention described above, aconvex portion which extends in the circumferential direction maypreferably be provided at a center in a width direction on the outerperipheral surface of the seal ring, and a portion closer to the highpressure side than the convex portion may be the concave portion.

Note that, in each of these aspects of the present invention, the “highpressure side” denotes one side where a pressure is high when a pressuredifference is created between two sides of the sealing device, and the“low pressure side” denotes another side where the pressure is low whenthe pressure difference is created between the two sides of the sealingdevice.

Also in each of these sealing devices, the seal ring is pressed towardsthe outer peripheral surface side by the metal spring. Accordingly, evenin a condition in which the fluid pressure is not applied (the pressuredifference is not created) or the fluid pressure is almost not applied(the pressure difference is almost not created), the seal ring iscontact with the inner peripheral surface of the shaft hole of thehousing, thereby exhibiting a sealing function. Consequently, it ispossible to hold the fluid pressure from immediately after the start ofincrease of the fluid pressure in the sealing target area. In addition,the concave portion is formed on the outer peripheral surface of theseal ring, and the fluid is introduced into the concave portion from thehigh pressure side. Accordingly, even when the fluid pressure isincreased, the fluid pressure acts towards the inner peripheral surfaceside within an area where the concave portion is provided. Consequently,it is possible to prevent the increase of pressure acting towards theouter peripheral surface side via the seal ring due to the increase ofthe fluid pressure, thereby making it possible to suppress a slidingtorque.

e.

Since the metal spring is provided so as to be placed along the innerperipheral surface of the seal ring in the state in which the gap isformed between the metal spring and the groove bottom surface of theannular groove, the metal spring is hardly influenced by eccentricity ofthe shaft and the housing. In addition, the seal ring and the metalspring would not rotate relative to each other. Consequently, the sealring and the metal spring would not slide relative to each other; hencethe inner peripheral surface side of the seal ring would not be abradeddue to sliding.

In the case where the configuration is adopted in which a guide portionwhich positions the metal spring in the axial direction is formed on theinner peripheral surface of the seal ring, it becomes possible toprevent the metal spring from being displaced in the axial direction.Consequently, the seal ring can be pressed towards the outer peripheralsurface side stably by the metal spring.

In addition, by providing the protrusion (the first protrusion) whichprevents the metal spring from being detached to the inner peripheralsurface side at the tip of the guide portion, it becomes possible toprevent the metal spring from being detached from the seal ring, whenthe seal ring is attached to the annular groove or the like.

In addition, in the case where the configuration is adopted in which theabutment portion is provided at one position of the seal ring in thecircumferential direction, and the protrusions (the second protrusions)which restrict the movement of the metal spring in the circumferentialdirection are provided on the inner peripheral surface on both sides ofthe abutment portion, it is possible to prevent positional displacementof the metal spring relative to the seal ring in the circumferentialdirection. Accordingly, it becomes possible to exercise a stable sealingperformance.

Advantageous Effects of Invention

As described thus far, according to the present invention, it ispossible to exercise the sealing function even in a condition in whichthe fluid pressure is low while suppressing the sliding torque.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a partially cutaway cross-sectional view of a sealing deviceaccording to a first example of the present invention.

FIG. 2 is a view showing an outer peripheral ring according to the firstexample of the present invention when viewed from an outer peripheralsurface side.

FIG. 3 is a side view of the outer peripheral ring according to thefirst example of the present invention.

FIG. 4 is a partially cutaway perspective view of the outer peripheralring according to the first example of the present invention.

FIG. 5 is a schematic cross-sectional view showing a sealing deviceaccording to the first example of the present invention in a no-loadcondition.

FIG. 6 is a schematic cross-sectional view showing the sealing deviceaccording to the first example of the present invention in the no-loadcondition.

FIG. 7 is a schematic cross-sectional view showing the sealing deviceaccording to the first example of the present invention in ahigh-pressure condition.

FIG. 8 is a partially cutaway perspective view of an outer peripheralring according to a modification of the first example of the presentinvention.

FIG. 9 is a schematic cross-sectional view showing a sealing deviceaccording to the modification of the first example of the presentinvention in a no-load condition.

FIG. 10 is a schematic cross-sectional view showing the sealing deviceaccording to the modification of the first example of the presentinvention in the no-load condition.

FIG. 11 is a partially cutaway cross-sectional view showing a sealingdevice according to a second example of the present invention.

FIG. 12 is a side view of a seal ring according to the second example ofthe present invention.

FIG. 13 is a side view of the seal ring according to the second exampleof the present invention.

FIG. 14 is a partially cutaway perspective view of the sealing deviceaccording to the second example of the present invention.

FIG. 15 is a schematic cross-sectional view of the seal ring accordingto the second example of the present invention.

FIG. 16 is a schematic cross-sectional view of the seal ring accordingto the second example of the present invention.

FIG. 17 is a schematic cross-sectional view showing the sealing deviceaccording to the second example of the present invention in a no-loadcondition.

FIG. 18 is a schematic cross-sectional view showing the sealing deviceaccording to the second example of the present invention in the no-loadcondition.

FIG. 19 is a schematic cross-sectional view showing the sealing deviceaccording to the second example of the present invention in ahigh-pressure condition.

FIG. 20 is a partially cutaway perspective view of a seal ring accordingto a first modification of the second example of the present invention.

FIG. 21 is a partially cutaway perspective view of a seal ring accordingto a second modification of the second example of the present invention.

FIG. 22 is a schematic cross-sectional view showing a sealing deviceaccording to a third modification of the second example of the presentinvention in a high-pressure condition.

FIG. 23 is a partially cutaway perspective view of a seal ring accordingto a fourth modification of the second example of the present invention.

FIG. 24 is a partially cutaway perspective view of a seal ring accordingto a fifth modification of the second example of the present invention.

FIG. 25 is a schematic cross-sectional view showing a sealing deviceaccording to a sixth modification of the second example of the presentinvention.

FIG. 26 is a partially cutaway cross-sectional view of a sealing deviceaccording to a third example of the present invention.

FIG. 27 is a side view of a seal ring according to the third example ofthe present invention.

FIG. 28 is a partially cutaway perspective view of the sealing deviceaccording to the third example of the present invention.

FIG. 29 is a schematic cross-sectional view of the seal ring accordingto the third example of the present invention.

FIG. 30 is a schematic cross-sectional view of the seal ring accordingto the third example of the present invention.

FIG. 31 is a schematic cross-sectional view showing the sealing deviceaccording to the third example of the present invention in ahigh-pressure condition.

FIG. 32 is a partially cutaway cross-sectional view of a sealing deviceaccording to a fourth example of the present invention.

FIG. 33 is a schematic cross-sectional view showing a seal ringaccording to a conventional art in a condition in which a hydraulicpressure is not held.

FIG. 34 is a schematic cross-sectional view showing the seal ringaccording to the conventional art in a condition in which the hydraulicpressure is held.

DESCRIPTION OF EMBODIMENTS

Hereinafter, modes for carrying out the present invention will beexemplarily described in detail based on examples thereof with referenceto the drawings. However, the dimensions, materials, shapes, relativearrangements and so on of constituent parts described in the examplesare not intended to limit the scope of the present invention to thesealone in particular unless specifically described. Note that a sealingdevice according to each of the present examples is used for the purposeof sealing an annular gap between a shaft and a housing which rotaterelative to each other in order to hold a hydraulic pressure in atransmission for automobiles such as AT and CVT. In addition, in thefollowing description, a “high pressure side” denotes one side where apressure is high when a pressure difference is created between two sidesof the sealing device, and a “low pressure side” denotes another sidewhere the pressure is low when the pressure difference is createdbetween the two sides of the sealing device.

First Example

With reference to FIGS. 1 to 7, a sealing device according to a firstexample of the present invention will be described.

<Configuration of Sealing Device>

With reference to FIGS. 1 and 5 to 7, in particular, the configurationof the sealing device according to the first example of the presentinvention will be described. A sealing device 100 according to thepresent example is attached to an annular groove 410 provided on anouter periphery of a shaft 400, and seals an annular gap between theshaft 400 and a housing 500 (an inner peripheral surface of a shaft holein the housing 500 through which the shaft 400 is inserted) which rotaterelative to each other. With this, the sealing device 100 holds a fluidpressure in a sealing target area configured such that the fluidpressure (a hydraulic pressure in the present example) changes. Herein,in the present example, the fluid pressure in the right area in each ofFIGS. 5 to 7 is configured to change, and the sealing device 100 plays arole in holding the fluid pressure in the sealing target area on theright in the drawing. Note that, in a condition in which an engine of anautomobile is stopped, the fluid pressure in the sealing target area islow and a no-load condition is created, and when the engine is started,the fluid pressure in the sealing target area increases.

The sealing device 100 according to the present example is constitutedof a seal ring 200 that is made of resin such as polyetheretherketone(PEEK), polyphenylene sulfide (PPS), or polytetrafluoroethylene (PTFE),and a metal spring 300. For the metal spring 300 in the present example,a C-ring, in which a cut-out is made at one place on an annular memberin a circumferential direction, is used.

In a state in which the seal ring 200 is combined with the metal spring300, the circumference of an outer peripheral surface of the seal ring200 is configured to be longer than the circumference of the innerperipheral surface of the shaft hole of the housing 500. Note that thecircumference of the outer peripheral surface of the seal ring 200itself is configured to be shorter than the circumference of the innerperipheral surface of the shaft hole of the housing 500, and thusconfigured to have no interference. Consequently, when the metal spring300 is not attached and an external force is not applied, the outerperipheral surface of the seal ring 200 does not make contact with theinner peripheral surface of the shaft hole of the housing 500.

<Seal Ring>

With reference to FIGS. 1 to 4, in particular, the seal ring 200according to the first example of the present invention will bedescribed in detail. On the seal ring 200, an abutment portion 210 isprovided at one position in a circumferential direction. In addition, aplurality of concave portions 220 for introducing a fluid is formed onthe outer peripheral surface of the seal ring 200 at intervals in thecircumferential direction. Further, on an inner peripheral surface ofthe seal ring 200, protrusions 223 and 224 as guide portions whichposition the metal spring 300 in an axial direction (a direction of acentral axis of the shaft 400; the same shall apply hereinafter) areprovided. The protrusions 223 and 224 are provided on a side of one oftwo side surfaces of the seal ring 200 and on a side of another of thetwo side surfaces thereof, respectively, so as to be provided on bothsides of the metal spring 300. A plurality of the protrusions 223 and224 are provided at intervals in the circumferential direction.

Note that the seal ring 200 according to the present example has theconfiguration in which the abutment portion 210, a plurality of theconcave portions 220, and a plurality of the protrusions 223 and 224 areformed on an annular member having a rectangular cross section. However,this is only a description of the shape, and this does not necessarilymean that an annular member having the rectangular cross section is usedas a material and a process to form an abutment portion 210, a pluralityof concave portions 220, and a plurality of protrusions 223 and 224 isapplied on this material. As a matter of course, it is also possible toform an abutment portion 210, a plurality of concave portions 220, and aplurality of protrusions 223 and 224 by applying a cutting-work aftermolding an annular member having a rectangular cross section. However,for example, a plurality of concave portions 220 may be formed byapplying a cutting-work after a member having an abutment portion 210and a plurality of protrusions 223 and 224 is molded in advance; henceproduction method is not particularly limited.

The abutment portion 210 employs so-called a special step cut in whichthe abutment portion 210 is cut to have a step-like shape when viewedfrom each of an outer peripheral surface side and both of side wallsurface sides. Accordingly, in the seal ring 200, a first engagementconvex portion 211 a and a first engagement concave portion 212 a areprovided on an outer peripheral side on one of two sides separated by acutoff portion, and a second engagement concave portion 212 b, withwhich the first engagement convex portion 211 a is engaged, and a secondengagement convex portion 211 b, with which the first engagement concaveportion 212 a is engaged, are provided on an outer peripheral side onanother of the two sides. Since the special step cut is a well-knowntechnique, the detailed description thereof will be omitted, but itshould be noted that the special step cut has a characteristic such thata stable sealing performance can be maintained even when thecircumference of the seal ring 200 changes due to thermalexpansion/contraction. Note that although the case of the special stepcut is described as an example of the abutment portion 210 thus far, theabutment portion 210 is not limited thereto, and it is also possible toadopt a straight cut or a bias cut. Note that, in a case where amaterial having low elasticity (PTFE or the like) is adopted as amaterial for the seal ring 200, the seal ring 200 may be made endlesswithout providing an abutment portion 210.

A plurality of the concave portions 220 are formed at intervals in thecircumferential direction. Note that, in the present example, aplurality of the concave portions 220 are provided at regular intervalsexcept in the vicinity of the abutment portion 210. In addition, thelength of the concave portion 220 in the circumferential direction isconfigured to be relatively long, and the length of a portion betweenthe two concave portions 220 in the circumferential direction isconfigured to be shorter than the length of the concave portion 220 inthe circumferential direction except in the vicinity of the abutmentportion 210. Hereinafter, the portion between the two concave portions220 is referred to as a rib 221. With the above configuration, theconcave portions 220 are formed over the almost entire region in thecircumferential direction. That is, the concave portions 220 are formedover the entire region in the circumferential direction except for theportion where the abutment portion 210 is formed and the portions wherea plurality of the ribs 221, each having a short length in thecircumferential direction, is formed. In addition, both side surfaces ofthe rib 221 in the present example are configured to be perpendicular toa bottom surface of the concave portion 220.

In addition, the concave portion 220 is formed so as to extend from oneend portion (a high pressure side (H) as will be described later) to aposition which does not reach another end portion (a low pressure side(L) as will be described later). More specifically, the concave portion220 is formed so as to extend to the position in the vicinity of theother end portion. Hereinafter, a portion on the other side (the lowpressure side (L)) on the outer peripheral surface side of the seal ring200 where the concave portion 220 is not formed is referred to as a lowpressure side convex portion 222. Note that, with regard to the depth ofthe concave portion 220, the rigidity of the portions provided with therib 221 and the low pressure side convex portion 222 is higher as theconcave portion 220 is shallower. On the other hand, the rib 221 and thelow pressure side convex portion 222 become abraded due to sliding;hence the depth of the concave portion 220 becomes shallower over time.Accordingly, when the depth of the concave portion 220 becomesexcessively shallow, a fluid may not be introduced. To cope with this,it is preferable to set the initial depth of the concave portion 220 inconsideration of both of the rigidity and maintaining the introductionof the fluid even when the temporal wear progresses. For example, in thecase where the thickness of the seal ring 200 is 1.7 mm, the depth ofthe concave portion 220 is preferably set to 0.1 mm or more and 0.3 mmor less, approximately. With regard to the width of the concave portion220 (the width in the axial direction), the width of the low pressureside convex portion 222 becomes narrower as the width of the concaveportion 220 is made wider. Although a torque can be reduced more as thewidth is set narrower, sealing performance and durability may bedegraded if the width is set excessively narrow. To cope with this, itis desirable to reduce the width as much as possible to the extent thatthe sealing performance and the durability can be maintained inaccordance with a use environment or the like. For example, in the casewhere the overall length of the width of the seal ring 200 (the width inthe axial direction) is 1.9 mm, the width of the low pressure sideconvex portion 222 is preferably set to 0.3 mm or more and 0.7 mm orless, approximately. In addition, the width of the rib 221 in thecircumferential direction is preferably set to 0.3 mm or more and 0.7 mmor less, approximately.

<Mechanism During Use of Sealing Device>

With reference to FIGS. 5 to 7, in particular, the mechanism during useof the sealing device 100 according to the present example will bedescribed. Each of FIGS. 5 and 6 shows a no-load condition in whichthere is no pressure difference (or there is almost no pressuredifference) between the left and right areas separated by the sealingdevice 100, after the engine has stopped. Note that FIG. 5 is aschematic cross-sectional view (a cross-sectional view including theaxis of the shaft 400) of a portion provided with the concave portion220 on the seal ring 200, and FIG. 6 is a schematic cross-sectional view(a cross-sectional view including the axis of the shaft 400) of aportion provided with the rib 221 on the seal ring 200. The seal ring200 in FIG. 5 corresponds to an AA cross section in FIG. 3, and the sealring 200 in FIG. 6 corresponds to a BB cross section in FIG. 3. FIG. 7shows a condition in which the engine is started, and the fluid pressurein the right area is increased and became higher than the fluid pressurein the left area separated by the sealing device 100. Note that FIG. 7is a schematic cross-sectional view (a cross-sectional view includingthe axis of the shaft 400) of the portion provided with the concaveportion 220 on the seal ring 200. The seal ring 200 in FIG. 7corresponds to the AA cross section in FIG. 3.

In a state in which the sealing device 100 is attached to the annulargroove 410, the metal spring 300 exhibits the function of pressing theseal ring 200 towards the outer peripheral surface side by its ownexpansive force. Consequently, portions of the outer peripheral surfaceof the seal ring 200 except for the concave portions 220, namelyportions provided with the rib 221 and the low pressure side convexportion 222 maintain contact with the inner peripheral surface of theshaft hole of the housing 500.

In a condition in which the engine is started and the pressuredifference is created, as shown in FIG. 7, the seal ring 200 is in astate in which it is in close contact with the side wall surface on thelow pressure side (L) of the annular groove 410 by the fluid pressurefrom the high pressure side (H). Note that it goes without saying thatthe seal ring 200 maintains a state in which it is in contact with (itslides against) the inner peripheral surface of the shaft hole of thehousing 500.

<Advantages of the Sealing Device According to the Present Example>

According to the sealing device 100 of the present example, the sealring 200 is pressed towards the outer peripheral surface side by themetal spring 300. Accordingly, even in a condition in which the fluidpressure is not applied (the pressure difference is not created), or thefluid pressure is almost not applied (the pressure difference is almostnot created), the seal ring 200 is in contact with the inner peripheralsurface of the shaft hole of the housing 500. Note that an annularcontinuous sealing surface is formed by the outer peripheral surface ofthe rib 221, the outer peripheral surface of the low pressure sideconvex portion 222, and the outer peripheral surface of the portion inthe vicinity of the abutment portion 210 where the concave portion 220is not formed. Accordingly, as long as the seal ring 200 maintains astate in which it is in close contact with the side wall surface on thelow pressure side (L) of the annular groove 410, the sealing function isexhibited. Consequently, it is possible to hold the fluid pressure fromimmediately after the start of increase of the fluid pressure in thesealing target area. That is, as for an engine having an idling stopfunction, it is possible to hold the hydraulic pressure from immediatelyafter the start of increase of hydraulic pressure on the sealing targetarea side when the engine is started by pressing an accelerator pedalfrom an engine stop condition.

Generally speaking, in a case of a seal ring made of resin, a functionof suppressing leakage of a fluid is not exhibited so well. However, inthe present example, because the seal ring 200 is pressed towards theouter peripheral surface side by the metal spring 300, the function ofsuppressing the leakage of the fluid is exhibited to a certain extent.Accordingly, it becomes possible to maintain the state in which thepressure difference is present for a while even after an action of apump or the like has stopped due to the stop of the engine.Consequently, in the engine having the idling stop function, in a casewhere a period of the engine stopping state is not too long, it ispossible to maintain the state in which the pressure difference ispresent; hence, when the engine is re-started, it is possible tosuitably hold the fluid pressure from immediately after the re-start.

In a condition in which considerable time has elapsed since the stop ofthe engine, the fluid pressure no longer acts (the pressure differencebecomes zero). In this case, the seal ring 200 may move away from theside wall surface of the annular groove 410 (the side wall surface onthe low pressure side (L) when the pressure difference is present).Accordingly, the leakage of the fluid may occur. However, as describedabove, in the case where the period of the engine stop state is not toolong, it is possible to maintain the condition in which the pressuredifference is present; hence it is possible to maintain the state inwhich the seal ring 200 is in close contact with the side wall surfaceon the low pressure side (L) of the annular groove 410. Consequently,even in a low-load condition, the function of suppressing the leakage ofthe fluid is exhibited.

In addition, a plurality of the concave portions 220 are formed on theouter peripheral surface of the seal ring 200, and the fluid isintroduced into a plurality of the concave portions 220 from the highpressure side (H). Accordingly, even when the fluid pressure isincreased, the fluid pressure acts towards the inner peripheral surfaceside in the region provided with the concave portions 220. Note thatarrows in FIG. 7 show a state in which the fluid pressure is acting onthe seal ring 200. With this, in the sealing device 100 according to thepresent example, it is possible to suppress the increase of the pressuretowards the outer peripheral surface side by the seal ring 200 due tothe increase of the fluid pressure, thereby making it possible tosuppress the sliding torque.

In addition, since a plurality of the concave portions 220 are formed atintervals in the circumferential direction, the portion (the rib 221)between two concave portions 220 makes contact with the inner peripheralsurface of the shaft hole of the housing 500. Further, by providing aplurality of the ribs 221, it is possible to suppress a degradation inthe rigidity of the seal ring 200 as compared with a case where the ribs221 are not provided. Consequently, it is possible to prevent the sealring 200 from being tilted within the annular groove 410, and stabilizean attachment state of the seal ring 200. Note that, in a case where aconfiguration is adopted in which a plurality of the ribs 221 is notprovided, it is anticipated that the seal ring 200 may be tilted incounter-clockwise direction in FIGS. 5 and 7.

In addition, in the present example, the concave portions 220 are formedover the entire periphery except in the vicinity of the abutment portion210 and the portions provided with a plurality of the ribs 221 with ashort length in the circumferential direction, and are formed so as toextend from the end portion on the high pressure side (H) to thevicinity of the end portion on the low pressure side (L). As described,in the present example, by providing the concave portions 220 over alarge area of the outer peripheral surface of the seal ring 200, it ispossible to reduce a sliding area between the seal ring 200 and theinner peripheral surface of the shaft hole of the housing 500 as much aspossible, thereby significantly reducing the sliding torque. Note thatthe sliding area between the seal ring 200 and the inner peripheralsurface of the shaft hole of the housing 500 is sufficiently smallerthan a contact area between the seal ring 200 and the side wall surfaceon the low pressure side (L) of the annular groove 410. With thisconfiguration, it is possible to prevent the seal ring 200 from slidingrelative to the side wall surface on the low pressure side (L) of theannular groove 410. Consequently, in the seal ring 200 according to thepresent example, because it is the outer peripheral surface side that issliding, a lubricating film made of a sealing target fluid (an oil filmin the present example) is formed more easily as compared with a casewhere the sealing ring slides against the side wall surface of theannular groove; hence it becomes possible to further reduce the slidingtorque.

As described, since it is possible to realize the reduction of slidingtorque, it becomes possible to suppress the generation of heat due tosliding; hence it becomes possible to suitably use the sealing device100 according to the present example even under high-speed andhigh-pressure environmental conditions.

Further, in the present example, since the metal spring 300 is providedso as to extend along the inner peripheral surface of the seal ring 200in a state in which a gap is formed between the metal spring 300 and thegroove bottom surface of the annular groove 410, the metal spring 300 ishardly influenced by eccentricity of the shaft 400 and the housing 500.In addition, the seal ring 200 and the metal spring 300 do not rotaterelative to each other. Consequently, the seal ring 200 and the metalspring 300 do not slide relative to each other; hence the innerperipheral surface side of the seal ring 200 would not be abraded due tosliding.

In addition, the metal spring 300 is positioned in the axial directionby the protrusions 223 and 224. Consequently, the seal ring 200 isstably pressed towards the outer peripheral surface side by the metalspring 300.

(Modification of Seal Ring)

In the above example, the case where a plurality of the protrusions 223and 224 are formed on the inner peripheral surface of the seal ring 200is described as an example of the guide portion that positions the metalspring 300 in the axial direction. As described in the above example, byadopting the configuration in which a plurality of the protrusions 223and 224 are provided at intervals in the circumferential direction andthe protrusion 223 and the protrusion 224 are disposed at differentpositions in the circumferential direction, it becomes possible toeasily form the protrusions 223 and 224 by molding that uses a die. Thatis, each of the protrusions 223 and 224 does not have an undercut in theaxial direction.

However, the configuration of the guide portion that positions the metalspring 300 in the axial direction is not limited to the configurationdescribed in the above example. For example, as shown in FIGS. 8 and 9,a groove 225 may be formed along the inner peripheral surface of theseal ring 200, and the metal spring 300 may be fitted in the groove 225.In this case, the groove 225 may be formed on the inner peripheralsurface of the seal ring 200 by cutting work. In a case where difficultyin cutting arises, a substantially annular groove 225 may be formedexcluding the vicinity of the abutment portion. In this case, the metalspring 300, which is a C-ring, may be fitted in the groove 225 such thatthe cut-out formed at one place in the circumferential direction ispositioned in the vicinity of the abutment portion. Note that, in FIGS.8 and 9, the configuration other than the groove 225 is the same as theconfiguration described in the above example; hence the same constituentparts are designated by the same reference numerals and the descriptionthereof is omitted.

In addition, the C-ring has been described as an example of the metalspring 300, but the metal spring 300 is not limited to the C-ring. Forexample, an annular coil spring such as a metal spring 300 a shown inFIG. 10 may also be used. Note that, in FIG. 10, the configuration otherthan the groove 225 and the metal spring 300 a is the same as theconfiguration described in the above example; hence the same constituentparts are designated by the same reference numerals, and the descriptionthereof is omitted.

Second Example

With reference to FIGS. 11 to 19, a sealing device according to a secondexample of the present invention will be described.

<Configuration of Sealing Device>

With reference to FIGS. 11 and 14 to 19, in particular, theconfiguration of the sealing device according to the second example ofthe present invention will be described. A sealing device 100 accordingto the present example is attached to an annular groove 410 provided onan outer periphery of a shaft 400, and seals an annular gap between theshaft 400 and a housing 500 (an inner peripheral surface of a shaft holein the housing 500 through which the shaft 400 is inserted) which rotaterelative to each other. With this, the sealing device 100 holds a fluidpressure in a sealing target area configured such that the fluidpressure (a hydraulic pressure in the present example) changes. Herein,in the present example, the fluid pressure in the right area in each ofFIGS. 17 to 19 is configured to change, and the sealing device 100 playsa role in holding the fluid pressure in the sealing target area on theright in the drawing. Note that, in a condition in which an engine of anautomobile is stopped, the fluid pressure in the sealing target area islow and a no-load condition is created, and when the engine is started,the fluid pressure in the sealing target area increases.

The sealing device 100 according to the present example is constitutedof a seal ring 200 that is made of resin such as polyetheretherketone(PEEK), polyphenylene sulfide (PPS), or polytetrafluoroethylene (PTFE),and a metal spring 300. For the metal spring 300 in the present example,a C-ring, in which a cut-out is made at one place on an annular memberin a circumferential direction, is used.

In a state in which the seal ring 200 is combined with the metal spring300, the circumference of an outer peripheral surface of the seal ring200 is configured to be longer than the circumference of the innerperipheral surface of the shaft hole of the housing 500. Note that thecircumference of the outer peripheral surface of the seal ring 200itself is configured to be shorter than the circumference of the innerperipheral surface of the shaft hole of the housing 500, and thusconfigured to have no interference. Consequently, when the metal spring300 is not attached and an external force is not applied, the outerperipheral surface of the seal ring 200 does not make contact with theinner peripheral surface of the shaft hole of the housing 500.

<Seal Ring>

With reference to FIGS. 11 to 16, in particular, the seal ring 200according to the second example of the present invention will bedescribed in detail. Note that FIGS. 12 and 13 are side views of theseal ring 200 according to the present example. FIG. 12 corresponds to aview when the seal ring 200 is seen from the bottom side of the drawingin FIG. 11, and FIG. 13 corresponds to a view when the seal ring 200 isseen from the top side of the drawing in FIG. 11. FIG. 14 is a partiallycutaway perspective view of the vicinity of an abutment portion of thesealing device according to the present example. FIGS. 15 and 16 areschematic cross-sectional view of the seal ring 200 according to thepresent example. FIG. 15 is an AA cross section in FIG. 13, and FIG. 16is a BB cross section in FIG. 13. Note that, in FIGS. 15 and 16, aposition of the metal spring 300 in its attachment state is depicted indotted-lines.

On the seal ring 200, an abutment portion 210 is provided at oneposition in a circumferential direction. In addition, a plurality ofconcave portions 220 for introducing a fluid is formed on the outerperipheral surface of the seal ring 200 at intervals in thecircumferential direction.

In addition, on an inner peripheral surface of the seal ring 200, guideprotrusions 231 and 232 as guide portions which position the metalspring 300 in an axial direction (a direction of a central axis of theshaft 400) are provided. The guide protrusions 231 and 232 are providedon a side of one of two side surfaces of the seal ring 200 and on a sideof another of the two side surfaces thereof, respectively, so as to beprovided on both sides of the metal spring 300. A plurality of the guideprotrusions 231 and 232 are provided at intervals in the circumferentialdirection. Note that the guide protrusions 231 and 232 are provided suchthat they protrude towards the inner peripheral surface side.

In addition, first protrusions 231 a and 232 a which prevent the metalspring 300 from being detached to the inner peripheral surface side areprovided at a tip of the guide protrusion 231 and at a tip of the guideprotrusion 232, respectively. The first protrusions 231 a and 232 a areprovided such that they protrude in the axial direction and towards theinner peripheral surface side.

Further, second protrusions 233 which restrict a movement of the metalspring 300 in the circumferential direction are provided on the innerperipheral surface on both sides of the abutment portion 210 of the sealring 200. Note that the metal spring 300 is attached to the innerperipheral surface side of the seal ring 200 so that two ends separatedby the cut-out at one place in the circumferential direction compress apair of the second protrusions 233 therebetween (see FIG. 14). Withthis, the ends of the metal spring 300 abut the second protrusions 233,thereby restricting the movement of the metal spring in thecircumferential direction.

Note that the seal ring 200 according to the present example has theconfiguration in which the abutment portion 210, a plurality of theconcave portions 220, a plurality of the guide protrusions 231 and 232provided with the first protrusions 231 a and 232 a respectively, andthe pair of second protrusions 233 are formed on an annular memberhaving a rectangular cross section. However, this is only a descriptionof the shape, and this does not necessarily mean that an annular memberhaving the rectangular cross section is used as a material and a processto form an abutment portion 210, a plurality of concave portions 220, aplurality of the concave portions 220, a plurality of the guideprotrusions 231 and 232 provided with the first protrusions 231 a and232 a respectively, and the pair of second protrusions 233 is applied onthis material. As a matter of course, it is also possible to form anabutment portion 210, a plurality of concave portions 220, a pluralityof the concave portions 220, a plurality of the guide protrusions 231and 232 provided with the first protrusions 231 a and 232 arespectively, and the pair of second protrusions 233 by applying acutting-work after molding an annular member having a rectangular crosssection. However, for example, a plurality of concave portions 220 maybe formed by applying a cutting-work after a member having an abutmentportion 210, a plurality of the guide protrusions 231 and 232 providedwith the first protrusions 231 a and 232 a respectively, and the pair ofsecond protrusions 233 is molded in advance; hence production method isnot particularly limited.

The abutment portion 210 employs so-called a special step cut in whichthe abutment portion 210 is cut to have a step-like shape when viewedfrom each of an outer peripheral surface side and both of side wallsurface sides. Accordingly, in the seal ring 200, a first engagementconvex portion 211 a and a first engagement concave portion 212 a areprovided on an outer peripheral side on one of two sides separated by acutoff portion, and a second engagement concave portion 212 b, withwhich the first engagement convex portion 211 a is engaged, and a secondengagement convex portion 211 b, with which the first engagement concaveportion 212 a is engaged, are provided on an outer peripheral side onanother of the two sides. Since the special step cut is a well-knowntechnique, the detailed description thereof will be omitted, but itshould be noted that the special step cut has a characteristic such thata stable sealing performance can be maintained even when thecircumference of the seal ring 200 changes due to thermalexpansion/contraction. Note that although the case of the special stepcut is described as an example of the abutment portion 210 thus far, theabutment portion 210 is not limited thereto, and it is also possible toadopt a straight cut or a bias cut.

A plurality of the concave portions 220 are formed at intervals in thecircumferential direction. Note that, in the present example, aplurality of the concave portions 220 are provided at regular intervalsexcept in the vicinity of the abutment portion 210. In addition, thelength of the concave portion 220 in the circumferential direction isconfigured to be relatively long, and the length of a portion betweenthe two concave portions 220 in the circumferential direction isconfigured to be shorter than the length of the concave portion 220 inthe circumferential direction except in the vicinity of the abutmentportion 210. Hereinafter, the portion between the two concave portions220 is referred to as a rib 221. With the above configuration, theconcave portions 220 are formed over the almost entire region in thecircumferential direction. That is, the concave portions 220 are formedover the entire region in the circumferential direction except for theportion where the abutment portion 210 is formed and the portions wherea plurality of the ribs 221, each having a short length in thecircumferential direction, is formed. In addition, both side surfaces ofthe rib 221 in the present example are configured to be perpendicular toa bottom surface of the concave portion 220.

In addition, the concave portion 220 is formed so as to extend from oneend portion (a high pressure side (H) as will be described later) to aposition which does not reach another end portion (a low pressure side(L) as will be described later). More specifically, the concave portion220 is formed so as to extend to the position in the vicinity of theother end portion. Hereinafter, a portion on the other side (the lowpressure side (L)) on the outer peripheral surface side of the seal ring200 where the concave portion 220 is not formed is referred to as a lowpressure side convex portion 222. Note that, with regard to the depth ofthe concave portion 220, the rigidity of the portions provided with therib 221 and the low pressure side convex portion 222 is higher as theconcave portion 220 is shallower. On the other hand, the rib 221 and thelow pressure side convex portion 222 become abraded due to sliding;hence the depth of the concave portion 220 becomes shallower over time.Accordingly, when the depth of the concave portion 220 becomesexcessively shallow, a fluid may not be introduced. To cope with this,it is preferable to set the initial depth of the concave portion 220 inconsideration of both of the rigidity and maintaining the introductionof the fluid even when the temporal wear progresses. For example, in thecase where the thickness of the seal ring 200 is 1.7 mm, the depth ofthe concave portion 220 is preferably set to 0.1 mm or more and 0.3 mmor less, approximately. With regard to the width of the concave portion220 (the width in the axial direction), the width of the low pressureside convex portion 222 becomes narrower as the width of the concaveportion 220 is made wider. Although a torque can be reduced more as thewidth is set narrower, sealing performance and durability may bedegraded if the width is set excessively narrow. To cope with this, itis desirable to reduce the width as much as possible to the extent thatthe sealing performance and the durability can be maintained inaccordance with a use environment or the like. For example, in the casewhere the overall length of the width of the seal ring 200 (the width inthe axial direction) is 1.9 mm, the width of the low pressure sideconvex portion 222 is preferably set to 0.3 mm or more and 0.7 mm orless, approximately. In addition, the width of the rib 221 in thecircumferential direction is preferably set to 0.3 mm or more and 0.7 mmor less, approximately.

<Mechanism During Use of Sealing Device>

With reference to FIGS. 17 to 19, in particular, the mechanism duringuse of the sealing device 100 according to the present example will bedescribed. Each of FIGS. 17 and 18 shows a no-load condition in whichthere is no pressure difference (or there is almost no pressuredifference) between the left and right areas separated by the sealingdevice 100, after the engine has stopped. Note that FIG. 17 is aschematic cross-sectional view (a cross-sectional view including theaxis of the shaft 400) of a portion provided with the concave portion220 on the seal ring 200, and FIG. 18 is a schematic cross-sectionalview (a cross-sectional view including the axis of the shaft 400) of aportion provided with the rib 221 on the seal ring 200. The seal ring200 in FIG. 17 corresponds to a CC cross section in FIG. 13, and theseal ring 200 in FIG. 18 corresponds to a DD cross section in FIG. 13.FIG. 19 shows a condition in which the engine is started, and the fluidpressure in the right area is increased and became higher than the fluidpressure in the left area separated by the sealing device 100. Note thatFIG. 19 is a schematic cross-sectional view (a cross-sectional viewincluding the axis of the shaft 400) of the portion provided with theconcave portion 220 on the seal ring 200. The seal ring 200 in FIG. 19corresponds to the CC cross section in FIG. 13.

In a state in which the sealing device 100 is attached to the annulargroove 410, the metal spring 300 exhibits the function of pressing theseal ring 200 towards the outer peripheral surface side by its ownexpansive force. Consequently, portions of the outer peripheral surfaceof the seal ring 200 except for the concave portions 220, namelyportions provided with the rib 221 and the low pressure side convexportion 222 maintain contact with the inner peripheral surface of theshaft hole of the housing 500.

In a condition in which the engine is started and the pressuredifference is created, as shown in FIG. 19, the seal ring 200 is in astate in which it is in close contact with the side wall surface on thelow pressure side (L) of the annular groove 410 by the fluid pressurefrom the high pressure side (H). Note that it goes without saying thatthe seal ring 200 maintains a state in which it is in contact with (itslides against) the inner peripheral surface of the shaft hole of thehousing 500.

<Advantages of the Sealing Device According to the Present Example>

According to the sealing device 100 of the present example, the sealring 200 is pressed towards the outer peripheral surface side by themetal spring 300. Accordingly, even in a condition in which the fluidpressure is not applied (the pressure difference is not created), or thefluid pressure is almost not applied (the pressure difference is almostnot created), the seal ring 200 is in contact with the inner peripheralsurface of the shaft hole of the housing 500. Note that an annularcontinuous sealing surface is formed by the outer peripheral surface ofthe rib 221, the outer peripheral surface of the low pressure sideconvex portion 222, and the outer peripheral surface of the portion inthe vicinity of the abutment portion 210 where the concave portion 220is not formed. Accordingly, as long as the seal ring 200 maintains astate in which it is in close contact with the side wall surface on thelow pressure side (L) of the annular groove 410, the sealing function isexhibited. Consequently, it is possible to hold the fluid pressure fromimmediately after the start of increase of the fluid pressure in thesealing target area. That is, as for an engine having an idling stopfunction, it is possible to hold the hydraulic pressure from immediatelyafter the start of increase of hydraulic pressure on the sealing targetarea side when the engine is started by releasing a brake pedal orpressing an accelerator pedal from an engine stop condition.

Generally speaking, in a case of a seal ring made of resin, a functionof suppressing leakage of a fluid is not exhibited so well. However, inthe present example, because the seal ring 200 is pressed towards theouter peripheral surface side by the metal spring 300, the function ofsuppressing the leakage of the fluid is exhibited to a certain extent.Accordingly, it becomes possible to maintain the state in which thepressure difference is present for a while even after an action of apump or the like has stopped due to the stop of the engine.Consequently, in the engine having the idling stop function, in a casewhere a period of the engine stopping state is not too long, it ispossible to maintain the state in which the pressure difference ispresent; hence, when the engine is re-started, it is possible tosuitably hold the fluid pressure from immediately after the re-start.

In a condition in which considerable time has elapsed since the stop ofthe engine, the fluid pressure no longer acts (the pressure differencebecomes zero). In this case, the seal ring 200 may move away from theside wall surface of the annular groove 410 (the side wall surface onthe low pressure side (L) when the pressure difference is present).Accordingly, the leakage of the fluid may occur. However, as describedabove, in the case where the period of the engine stop state is not toolong, it is possible to maintain the condition in which the pressuredifference is present; hence it is possible to maintain the state inwhich the seal ring 200 is in close contact with the side wall surfaceon the low pressure side (L) of the annular groove 410. Consequently,even in a low-load condition, the function of suppressing the leakage ofthe fluid is exhibited.

In addition, a plurality of the concave portions 220 are formed on theouter peripheral surface of the seal ring 200, and the fluid isintroduced into a plurality of the concave portions 220 from the highpressure side (H). Accordingly, even when the fluid pressure isincreased, the fluid pressure acts towards the inner peripheral surfaceside in the region provided with the concave portions 220. Note thatarrows in FIG. 19 show a state in which the fluid pressure is acting onthe seal ring 200. With this, in the sealing device 100 according to thepresent example, it is possible to suppress the increase of the pressuretowards the outer peripheral surface side by the seal ring 200 due tothe increase of the fluid pressure, thereby making it possible tosuppress the sliding torque.

In addition, since a plurality of the concave portions 220 are formed atintervals in the circumferential direction, the portion (the rib 221)between two concave portions 220 makes contact with the inner peripheralsurface of the shaft hole of the housing 500. Further, by providing aplurality of the ribs 221, it is possible to suppress a degradation inthe rigidity of the seal ring 200 as compared with a case where the ribs221 are not provided. Consequently, it is possible to prevent the sealring 200 from being tilted within the annular groove 410, and stabilizean attachment state of the seal ring 200. Note that, in a case where aconfiguration is adopted in which a plurality of the ribs 221 is notprovided, it is anticipated that the seal ring 200 may be tilted incounter-clockwise direction in FIGS. 17 to 19.

In addition, in the present example, the concave portions 220 are formedover the entire periphery except in the vicinity of the abutment portion210 and the portions provided with a plurality of the ribs 221 with ashort length in the circumferential direction, and are formed so as toextend from the end portion on the high pressure side (H) to thevicinity of the end portion on the low pressure side (L). As described,in the present example, by providing the concave portions 220 over alarge area of the outer peripheral surface of the seal ring 200, it ispossible to reduce a sliding area between the seal ring 200 and theinner peripheral surface of the shaft hole of the housing 500 as much aspossible, thereby significantly reducing the sliding torque. Note thatthe sliding area between the seal ring 200 and the inner peripheralsurface of the shaft hole of the housing 500 is sufficiently smallerthan a contact area between the seal ring 200 and the side wall surfaceon the low pressure side (L) of the annular groove 410. With thisconfiguration, it is possible to prevent the seal ring 200 from slidingrelative to the side wall surface on the low pressure side (L) of theannular groove 410. Consequently, in the seal ring 200 according to thepresent example, because it is the outer peripheral surface side that issliding, a lubricating film made of a sealing target fluid (an oil filmin the present example) is formed more easily as compared with a casewhere the sealing ring slides against the side wall surface of theannular groove; hence it becomes possible to further reduce the slidingtorque.

As described, since it is possible to realize the reduction of slidingtorque, it becomes possible to suppress the generation of heat due tosliding; hence it becomes possible to suitably use the sealing device100 according to the present example even under high-speed andhigh-pressure environmental conditions.

Further, in the present example, since the metal spring 300 is providedso as to extend along the inner peripheral surface of the seal ring 200in a state in which a gap is formed between the metal spring 300 and thegroove bottom surface of the annular groove 410, the metal spring 300 ishardly influenced by eccentricity of the shaft 400 and the housing 500.In addition, the seal ring 200 and the metal spring 300 do not rotaterelative to each other. Consequently, the seal ring 200 and the metalspring 300 do not slide relative to each other; hence the innerperipheral surface side of the seal ring 200 would not be abraded due tosliding.

In the present example, the guide protrusions 231 and 232 are providedon the inner peripheral surface of the seal ring 200 as the guideportions that position the metal spring 300 in the axial direction.Consequently, the seal ring 200 is stably pressed towards the outerperipheral surface side by the metal spring 300.

In addition, in the present example, a configuration is adopted in whichthe first protrusions 231 a and 232 a which prevent the metal spring 300from being detached to the inner peripheral surface side are provided atthe tips of the guide protrusion 231 and 232. Consequently, it becomespossible to prevent the metal spring 300 from being detached from theseal ring 200 at a time when the seal ring 200 with the metal ring 300attached thereto is being fitted into the annular groove 410 or in acase where disturbances or the like due to a pressure fluctuationoccurred during transportation or usage.

In addition, in the present example, a configuration is adopted in whichthe second protrusions 233 which restrict a movement of the metal spring300 in the circumferential direction are provided on the innerperipheral surface on both sides of the abutment portion 210 of the sealring 200. Consequently, it becomes possible to prevent positionaldisplacement of the metal spring 300 relative to the seal ring 200 inthe circumferential direction. Accordingly, it becomes possible toexercise a stable sealing performance.

(Modification of Seal Ring)

In the above example, the case has been described where a plurality ofthe concave portions 220 are provided at intervals in thecircumferential direction on the outer peripheral surface of the sealring 200 and the rib 221 s between the neighboring concave portions 220are configured to extend in the axial direction. However, thearrangement configuration of the concave portions 220 and the ribs 221is not limited to such configuration.

For example, as shown by a first modification in FIG. 20, a plurality ofribs 221 a may be provided such that they extend form the low pressureside (L) to the high pressure side (H) as they advance in a slidingdirection of the seal ring 200 with respect to the housing 500 (adirection of arrow R in FIG. 20). In this case, the fluid introducedinto concave portions 220 a due to the relative rotation of the housing500 and the seal ring 200 flows from the high pressure side (H) to thelow pressure side (L) and in a sliding direction of the housing 500 withrespect to the seal ring 200 aggressively (the fluid flows in adirection of arrow X in FIG. 20).

Accordingly, within the concave portion 220 a, the flow of the fluidconverges in the vicinity of a wedge-shaped apex formed by the lowpressure side convex portion 222 and the rib 221 a. As dynamic pressureis created by the convergence of the flow of the fluid, the seal ring200 is pressed towards the inner peripheral surface side. Consequently,with the help of the dynamic pressure as well, it becomes possible tosuppress the increase of the pressure towards the outer peripheralsurface side by the seal ring 200, thereby making it possible tosuppress the sliding torque. Note that the first modification can beapplied to any of the above described first and second examples, and themodification of the first example.

In addition, as shown by a second modification in FIG. 21, a pluralityof ribs 221 b may be provided such that they extend form the highpressure side (H) to the low pressure side (L) as they advance in asliding direction of the seal ring 200 with respect to the housing 500(a direction of arrow R in FIG. 21). In this case, the fluid introducedinto concave portions 220 b due to the relative rotation of the housing500 and the seal ring 200 flows from the low pressure side (L) to thehigh pressure side (H) and in a sliding direction of the housing 500with respect to the seal ring 200 aggressively (the fluid flows in adirection of arrow X in FIG. 21).

As described, the relative rotation of the housing 500 and the seal ring200 forces the fluid introduced into the concave portions 220 b toreturn to the high pressure side (H). Consequently, a leakage of thefluid can be suppressed. Note that the second modification can beapplied to any of the above described first and second examples, and themodification of the first example.

In addition, as shown by a third modification in FIG. 22, a convexportion 222 b may be provided on the outer peripheral surface of theseal ring 200 such that the convex portion 222 b extends in acircumferential direction, while it also extends to the high pressureside (H) and the low pressure side (L) alternately such that it extendsto positions that reach one end face in a width direction and positionsthat reach another end face in the width direction. More specifically,the convex portion 222 b is configured such that it serpentines in thecircumferential direction to form a wave shape.

With the provision of the convex portion 222 b, a plurality of concaveportions 220 c and 220 d are formed at intervals in the circumferentialdirection on both of the high pressure side (H) and the low pressureside (L) of the outer peripheral surface of the seal ring 200,respectively. The concave portions 220 c on the high pressure side (H)are configured so as to extend from an end portion on the high pressureside (H) to a position which does not reach an end portion on the lowpressure side (L), and exhibit a function to introduce the fluid fromthe high pressure side (H).

The convex portion 222 b formed on the outer peripheral surface of theseal ring 200 according to the present modification is formed such thatit extends in the circumferential direction while switching thepositions on the high pressure side (H) and the low pressure side (L)alternately. Accordingly, a position on the outer peripheral surface ofthe seal ring 200 that slides against the shaft hole of the housing 500would not be biased on the high pressure side (H) or the low pressureside (L). Consequently, it becomes possible to prevent the seal ring 200from being tilted within the annular groove 410, and stabilize theattachment state of the seal ring 200.

In addition, the plurality of concave portions 220 c are formed on theouter peripheral surface of the seal ring 200, and the fluid isintroduced into the plurality of concave portions 220 c from the highpressure side (H). Accordingly, even when the fluid pressure isincreased, the fluid pressure acts towards the inner peripheral surfaceside in the region provided with the concave portions 220 c. With this,in the present modification as well, it is possible to suppress theincrease of the pressure towards the outer peripheral surface side bythe seal ring 200 due to the increase of the fluid pressure, therebymaking it possible to suppress the sliding torque.

Furthermore, the seal ring 200 according to the present modification hasa structure that is symmetrical with respect to a central plane in thewidth direction (axial direction). Consequently, it is not necessary tocheck an attachment direction when attaching the seal ring 200, hencesuperior in attachability. In addition, it can be applied under acondition in which the high pressure side (H) and the low pressure side(L) alternate. Note that the third modification can be applied to any ofthe above described first and second examples, and the modification ofthe first example.

In addition, as shown by a fourth modification in FIG. 23, a convexportion 222 c may be provided on the outer peripheral surface of theseal ring 200 such that the convex portion 222 c extends in acircumferential direction, while it also extends to the high pressureside (H) and the low pressure side (L) alternately such that it reachespositions that reach one end face in a width direction and positionsthat reach another end face in the width direction. However, in thefourth modification, unlike with the above described third modification,the convex portion 222 c is configured so as to form a rectangular waveshape in the circumferential direction.

With the provision of the convex portion 222 c, a plurality of concaveportions 220 e and 220 f are formed at intervals in the circumferentialdirection on both of the high pressure side (H) and the low pressureside (L) of the outer peripheral surface of the seal ring 200,respectively. The concave portions 220 e on the high pressure side (H)are configured so as to extend from an end portion on the high pressureside (H) to a position which does not reach an end portion on the lowpressure side (L), and exhibit a function to introduce the fluid fromthe high pressure side (H).

It goes without saying that, also in the fourth modification, the sameeffects as those in the case of the third modification can be achieved.Note that the fourth modification can be applied to any of the abovedescribed first and second examples, and the modification of the firstexample.

In addition, as shown by a fifth modification in FIG. 24, a convexportion 222 d may be provided on the outer peripheral surface of theseal ring 200 such that the convex portion 222 d extends in acircumferential direction, while it also extends to the high pressureside (H) and the low pressure side (L) alternately such that it reachespositions that reach one end face in a width direction and positionsthat reach another end face in the width direction. However, in thefifth modification, unlike with the above described third modification,the convex portion 222 d is configured so as to form a triangular waveshape in the circumferential direction.

With the provision of the convex portion 222 d, a plurality of concaveportions 220 g and 220 h are formed at intervals in the circumferentialdirection on both of the high pressure side (H) and the low pressureside (L) of the outer peripheral surface of the seal ring 200,respectively. The concave portions 220 g on the high pressure side (H)are configured so as to extend from an end portion on the high pressureside (H) to a position which does not reach an end portion on the lowpressure side (L), and exhibit a function to introduce the fluid fromthe high pressure side (H).

It goes without saying that, also in the fifth modification, the sameeffects as those in the case of the third modification can be achieved.Note that the fifth modification can be applied to any of the abovedescribed first and second examples, and the modification of the firstexample.

In addition, as described in the above examples, the reason forproviding the plurality of concave portions 220 in the circumferentialdirection to provide the rib 221 between the two concave portions 220 isto prevent the seal ring from being tilted within the annular groove410.

However, as shown by a sixth modification in FIG. 25, the tilting of theseal ring 200 may be prevented by providing, on the outer peripheralsurface of the seal ring 200, one concave portion 220 over the entireperiphery except in the vicinity of the abutment portion 210, and notonly the low pressure side convex portion 222 but also a high pressureside convex portion 222 a on the high pressure side. However, as for thehigh pressure side convex portion 222 a, it is necessary to ensure a gapS between the high pressure side convex portion 222 a and the innerperipheral surface of the shaft hole of the housing 500 by making theprotrusion amount thereof smaller than that of the low pressure sideconvex portion 222. By securing the gap S in this manner, it becomespossible to introduce the fluid into the concave portion 220. Note that,similar to the low pressure side convex portion 222, the high pressureside convex portion 222 a may be provided over the entire peripheryexcept in the vicinity of the abutment portion 210 of the seal ring 200,or a plurality of the convex portions 222 a may be provided at intervalsin the circumferential direction. Note that the sixth modification canbe applied to any of the above described first and second examples, andthe modification of the first example.

(Others)

In the above second example, the case is shown in which the guideprotrusions 231 and 232 provided with the first protrusions 231 a and232 a respectively, and the second protrusions are all provided on theinner peripheral surface of the seal ring 200.

However, following configurations may be adopted depending on the usageenvironments. That is, one configuration may be adopted in which theguide protrusions 231 and 232 provided with the first protrusions 231 aand 232 a respectively are formed on the inner periphery of the sealring 200, whereas the second protrusions 233 are not. In addition,another configuration may be adopted in which the second protrusions 233are formed on the inner periphery of the seal ring 200, whereas theguide protrusions 231 and 232 are not. Furthermore, yet anotherconfiguration may be adopted in which the guide protrusions 231 and 232without the first protrusions 231 a and 232 a, and the secondprotrusions 233 are formed on the inner periphery of the seal ring 200.

Third Example

In FIGS. 26 to 31, a third example according to the present invention isshown. In the present example, basic configuration and operationsthereof are the same as those in the second example; hence the sameconstituent parts are designated by the same reference numerals, and thedescription thereof is omitted as appropriate.

<Configuration of Sealing Device>

With reference to FIGS. 26 and 18 to 31, in particular, theconfiguration of the sealing device according to the third example ofthe present invention will be described. A sealing device 100 accordingto the present example is attached to an annular groove 410 provided onan outer periphery of a shaft 400, and seals an annular gap between theshaft 400 and a housing 500 (an inner peripheral surface of a shaft holein the housing 500 through which the shaft 400 is inserted) which rotaterelative to each other. With this, the sealing device 100 holds a fluidpressure in a sealing target area configured such that the fluidpressure (a hydraulic pressure in the present example) changes. Herein,in the present example, the fluid pressure in the right area in FIG. 31is configured to change, and the sealing device 100 plays a role inholding the fluid pressure in the sealing target area on the right inthe drawing. Note that, in a condition in which an engine of anautomobile is stopped, the fluid pressure in the sealing target area islow and a no-load condition is created, and when the engine is started,the fluid pressure in the sealing target area increases.

The sealing device 100 according to the present example is constitutedof a seal ring 200 that is made of resin such as polyetheretherketone(PEEK), polyphenylene sulfide (PPS), or polytetrafluoroethylene (PTFE),and a metal spring 300. For the metal spring 300 in the present example,a C-ring, in which a cut-out is made at one place on an annular memberin a circumferential direction, is used.

In a state in which the seal ring 200 is combined with the metal spring300, the circumference of an outer peripheral surface of the seal ring200 is configured to be longer than the circumference of the innerperipheral surface of the shaft hole of the housing 500. Note that thecircumference of the outer peripheral surface of the seal ring 200itself is configured to be shorter than the circumference of the innerperipheral surface of the shaft hole of the housing 500, and thusconfigured to have no interference. Consequently, when the metal spring300 is not attached and an external force is not applied, the outerperipheral surface of the seal ring 200 does not make contact with theinner peripheral surface of the shaft hole of the housing 500.

<Seal Ring>

With reference to FIGS. 26 to 30, in particular, the seal ring 200according to the third example of the present invention will bedescribed in detail. Note that FIG. 28 is a partially cutawayperspective view of the vicinity of an abutment portion of the sealingdevice according to the present example. FIGS. 29 and 30 are schematiccross-sectional view of the seal ring 200 according to the presentexample. FIG. 29 is an AA cross section in FIG. 27, and FIG. 30 is a BBcross section in FIG. 27. Note that, in FIGS. 29 and 30, a position ofthe metal spring 300 in its attachment state is depicted indotted-lines.

On the seal ring 200, an abutment portion 210 is provided at oneposition in a circumferential direction. In addition, a convex portion250 which extends in the circumferential direction is provided at acenter in a width direction on the outer peripheral surface of the sealring 200. A pair of concave portions 260 is provided at both sides ofthe convex portion 250 in an axial direction (a direction of a centralaxis of the shaft 400).

In addition, on an inner peripheral surface of the seal ring 200, guideprotrusions 271 and 272 as guide portions which position the metalspring 300 in the axial direction are provided. The guide protrusions271 and 272 are provided on a side of one of two side surfaces of theseal ring 200 and on a side of another of the two side surfaces thereof,respectively, so as to be provided on both sides of the metal spring300. A plurality of the guide protrusions 271 and 272 are provided atintervals in the circumferential direction. Note that the guideprotrusions 271 and 272 are provided such that they protrude towards theinner peripheral surface side.

In addition, first protrusions 271 a and 272 a which prevent the metalspring 300 from being detached to the inner peripheral surface side areprovided at a tip of the guide protrusion 271 and at a tip of the guideprotrusion 272, respectively. The first protrusions 231 a and 232 a areprovided such that they protrude in the axial direction and towards theinner peripheral surface side.

Further, second protrusions 273 which restrict a movement of the metalspring 300 in the circumferential direction are provided on the innerperipheral surface on both sides of the abutment portion 210 of the sealring 200. Herein, the second protrusion 233 in the above describedsecond example is configured so as to extend in the axial direction,whereas the second protrusion 273 in the present example is configuredso as to have an engagement concave portion 273 a with which an endportion of the metal spring 300 is engaged. However, also in the presentexample, a configuration that is similar to the second protrusion 233described in the second example can be adopted.

Note that the seal ring 200 according to the present example has theconfiguration in which the abutment portion 210, the convex portion 250,the pair of concave portions 260, a plurality of the guide protrusions271 and 272 provided with the first protrusions 271 a and 272 arespectively, and the pair of second protrusions 273 are formed on anannular member having a rectangular cross section. However, this is onlya description of the shape, and this does not necessarily mean that anannular member having the rectangular cross section is used as amaterial and a process to form an abutment portion 210, a convex portion250, a pair of concave portions 260, a plurality of guide protrusions271 and 272 provided with first protrusions 271 a and 272 arespectively, and a pair of second protrusions 273 is applied on thismaterial. As a matter of course, it is also possible to form an abutmentportion 210, a convex portion 250, a pair of concave portions 260, aplurality of guide protrusions 271 and 272 provided with firstprotrusions 271 a and 272 a respectively, and a pair of secondprotrusions 273 by applying a cutting-work after molding an annularmember having a rectangular cross section. However, for example, aconvex portion 250 and a pair of concave portions 260 may be formed byapplying a cutting-work after a member having an abutment portion 210, aplurality of guide protrusions 271 and 272 provided with firstprotrusions 271 a and 272 a respectively, and a pair of secondprotrusions 273 is molded in advance; hence production method is notparticularly limited.

As for the abutment portion 210, similar to the above described firstand second examples, so-called a special step cut is employed in thepresent example as well in which the abutment portion 210 is cut to havea step-like shape when viewed from each of an outer peripheral surfaceside and both of side wall surface sides. With respect to the abutmentportion 210, since the configuration thereof is similar to that in thefirst or second example, the description thereof is omitted.

The pair of concave portions 260 is formed over the entire peripheryexcept in the vicinity of the abutment portion 210. A portion in thevicinity of the abutment portion 260 where the concave portion 260 isnot formed, and an outer peripheral surface of the convex portion 250are in plane with each other. Accordingly, an annular continuous sealingsurface is formed on an outer peripheral surface side of the seal ring200. That is, on the outer peripheral surface of the seal ring 200 andin a region except for the vicinity of the abutment portion 210, only anouter peripheral surface of the convex portion 250 slides against theinner peripheral surface of the shaft hole.

As for a width of the convex portion 250, although a torque can bereduced more as the width is set narrower, sealing performance anddurability may be degraded if the width is set excessively narrow. Tocope with this, it is desirable to reduce the width as much as possibleto the extent that the sealing performance and the durability can bemaintained in accordance with a use environment or the like. Forexample, in the case where the overall length of the width of the sealring 200 (the width in the axial direction) is 1.9 mm, the width of theconvex portion 250 is preferably set to 0.3 mm or more and 0.7 mm orless, approximately.

<Mechanism During Use of Sealing Device>

With reference to FIG. 31, in particular, the mechanism during use ofthe sealing device 100 according to the present example will bedescribed. FIG. 31 shows a condition in which the engine is started, andthe fluid pressure in the right area is increased and became higher thanthe fluid pressure in the left area separated by the sealing device 100.Note that the seal ring 200 in FIG. 31 corresponds to the CC crosssection in FIG. 27.

In a state in which the sealing device 100 is attached to the annulargroove 410, the metal spring 300 exhibits the function of pressing theseal ring 200 towards the outer peripheral surface side by its ownexpansive force. Consequently, a portion of the outer peripheral surfaceof the seal ring 200 except for the concave portions 260, namely aportion provided with the convex portion 250 maintains contact with theinner peripheral surface of the shaft hole of the housing 500.

In a condition in which the engine is started and the pressuredifference is created, as shown in FIG. 31, the seal ring 200 is in astate in which it is in close contact with the side wall surface on thelow pressure side (L) of the annular groove 410 by the fluid pressurefrom the high pressure side (H). Note that it goes without saying thatthe seal ring 200 maintains a state in which it is in contact with (itslides against) the inner peripheral surface of the shaft hole of thehousing 500.

<Advantages of the Sealing Device According to the Present Example>

Also in the sealing device 100 according to the present exampleconfigured as described above, the same effects as those in the case ofthe second example can be achieved.

Note that in the case of the sealing device 100 according to the presentexample, among the pair of concave portions 260 provided on the sealring 200, the fluid is introduced into the concave portion 260 on thehigh pressure side (H) from the high pressure side (H). Consequently,although a function of suppressing the increase of the pressure towardsthe outer peripheral surface side by the seal ring 200 due to theincrease of the fluid pressure may be inferior compared to the secondexample, the same effect as that in the case of the second example canbe achieved. Note that arrows in FIG. 31 show a state in which the fluidpressure is acting on the seal ring 200.

In addition, in the case of the seal ring 200 according to the presentexample, since the shape thereof is symmetrical with respect to acentral plane in the width direction, it is not necessary to check anattachment direction when attaching the seal ring 200 to the annulargroove 410. In addition, even under a condition in which the highpressure side (H) and the low pressure side (L) alternate, theadvantageous effects as described above can be exhibited.

Fourth Example

In FIG. 32, a fourth example according to the present invention isshown. In the present example, a configuration is described in which aplurality of ribs is further provided within the pair of concaveportions in the configuration of the above described third example.Other configuration and operations thereof are the same as those in thethird example; hence the same constituent parts are designated by thesame reference numerals, and the description thereof is omitted asappropriate.

The sealing device 100 according to the present example is alsoconstituted of a seal ring 200 that is made of resin and a metal spring300. The seal ring 200 according to the present example also has anabutment portion 210, a convex portion 250, a pair of concave portions260, a plurality of guide protrusions 271 and 272 provided with firstprotrusions 271 a and 272 a respectively, and a pair of secondprotrusions 273. Configurations of these are the same as those of theseal ring in the third example; hence the description thereof isomitted. Note that, although the guide protrusion 272 and the secondprotrusion 273 described in the third example are not depicted in FIG.32, the seal ring 200 according to the present example is also providedwith them. In addition, as for the abutment portion 210, although thecase is described where the special step cut is adopted in the presentexample as well, the abutment portion 210 is not limited thereto asdescribed in the first and second examples.

In the present example, a plurality of ribs 251 that are formed so as tobe connected with the convex portion 250 are provided within the pair ofconcave portions 260. The point that the ribs 251 are further providedis the only difference from the third example.

Also in the sealing device 100 according to the present exampleconfigured as described above, the same effects as those in the case ofthe sealing device 100 according to the third example can be achieved.In addition, in the present example, since the ribs 251 are provided,the rigidity of the sealing ring is high, especially the strength in atorsion direction. Consequently, even under a condition in which thepressure difference becomes large, the deformation of the seal ring 200is suppressed; hence the sealing performance can be exhibited stably.

REFERENCE SIGNS LIST

-   100: sealing device-   200: seal ring-   210: abutment portion-   211 a: first engagement convex portion-   211 b: second engagement convex portion-   212 a: first engagement concave portion-   212 b: second engagement concave portion-   220, 220 a, 220 b, 220 c, 220 d, 220 e, 220 f, 220 g, 220 h: concave    portion-   221, 221 a, 221 b: rib-   222: low pressure side convex portion-   222 a: high pressure side convex portion-   222 b, 222 c, 222 d: convex portion-   223, 224: protrusion-   225: groove-   231, 232, 271, 272: guide protrusion-   231 a, 232 a, 271 a, 272 a: first protrusion-   233, 273: second protrusion-   250: convex portion-   251: rib-   260: concave portion-   273 a: engagement concave portion-   400: shaft-   410: annular groove-   500: housing

1. A sealing device which is attached to an annular groove provided onan outer periphery of a shaft and holds a fluid pressure in a sealingtarget area by sealing an annular gap between the shaft and a housingrotating relative to each other, the sealing target area beingconfigured such that the fluid pressure changes, the sealing devicecomprising: a seal ring made of resin which is in close contact with aside wall surface on a low pressure side of the annular groove, andslides against an inner peripheral surface of a shaft hole in thehousing through which the shaft is inserted; and a metal spring which isprovided along an inner peripheral surface of the seal ring in a statein which a gap is formed between the metal spring and a groove bottomsurface of the annular groove, and presses the seal ring toward an outerperipheral surface side, wherein a concave portion is formed on an outerperipheral surface of the seal ring which extends from an end portion ona high pressure side of the outer peripheral surface to a position whichdoes not reach an end portion on a low pressure side of the outerperipheral surface, and introduces a fluid from the high pressure side.2. The sealing device according to claim 1, wherein a plurality of theconcave portions are formed at intervals in a circumferential direction.3. The sealing device according to claim 1, wherein a guide portionwhich positions the metal spring in an axial direction is formed on theinner peripheral surface of the seal ring.
 4. A sealing device which isattached to an annular groove provided on an outer periphery of a shaftand holds a fluid pressure in a sealing target area by sealing anannular gap between the shaft and a housing rotating relative to eachother, the sealing target area being configured such that the fluidpressure changes, the sealing device comprising: a seal ring made ofresin which is in close contact with a side wall surface on a lowpressure side of the annular groove, and slides against an innerperipheral surface of a shaft hole in the housing through which theshaft is inserted; and a metal spring which is provided along an innerperipheral surface of the seal ring in a state in which a gap is formedbetween the metal spring and a groove bottom surface of the annulargroove, and presses the seal ring toward an outer peripheral surfaceside, wherein a concave portion is formed on an outer peripheral surfaceof the seal ring which extends from an end portion on a high pressureside of the outer peripheral surface to a position which does not reachan end portion on a low pressure side of the outer peripheral surface,and introduces a fluid from the high pressure side, and a guide portionwhich positions the metal spring in an axial direction is formed on theinner peripheral surface of the seal ring, and a protrusion whichprevents the metal spring from being detached to an inner peripheralsurface side is provided at a tip of the guide portion.
 5. A sealingdevice which is attached to an annular groove provided on an outerperiphery of a shaft and holds a fluid pressure in a sealing target areaby sealing an annular gap between the shaft and a housing rotatingrelative to each other, the sealing target area being configured suchthat the fluid pressure changes, the sealing device comprising: a sealring made of resin which is in close contact with a side wall surface ona low pressure side of the annular groove, and slides against an innerperipheral surface of a shaft hole in the housing through which theshaft is inserted; and a metal spring which is provided along an innerperipheral surface of the seal ring in a state in which a gap is formedbetween the metal spring and a groove bottom surface of the annulargroove, and presses the seal ring toward an outer peripheral surfaceside, wherein a concave portion is formed on an outer peripheral surfaceof the seal ring which extends from an end portion on a high pressureside of the outer peripheral surface to a position which does not reachan end portion on a low pressure side of the outer peripheral surface,and introduces a fluid from the high pressure side, and an abutmentportion is provided at one position on the seal ring in acircumferential direction, and protrusions which restrict a movement ofthe metal spring in the circumferential direction are provided on theinner peripheral surface on both sides of the abutment portion.
 6. Asealing device which is attached to an annular groove provided on anouter periphery of a shaft and holds a fluid pressure in a sealingtarget area by sealing an annular gap between the shaft and a housingrotating relative to each other, the sealing target area beingconfigured such that the fluid pressure changes, the sealing devicecomprising: a seal ring made of resin which is in close contact with aside wall surface on a low pressure side of the annular groove, andslides against an inner peripheral surface of a shaft hole in thehousing through which the shaft is inserted; and a metal spring which isprovided along an inner peripheral surface of the seal ring in a statein which a gap is formed between the metal spring and a groove bottomsurface of the annular groove, and presses the seal ring toward an outerperipheral surface side, wherein a concave portion is formed on an outerperipheral surface of the seal ring which extends from an end portion ona high pressure side of the outer peripheral surface to a position whichdoes not reach an end portion on a low pressure side of the outerperipheral surface, and introduces a fluid from the high pressure side,a guide portion which positions the metal spring in an axial directionis formed on the inner peripheral surface of the seal ring, and a firstprotrusion which prevents the metal spring from being detached to aninner peripheral surface side is provided at a tip of the guide portion,and an abutment portion is provided at one position on the seal ring ina circumferential direction, and second protrusions which restrict amovement of the metal spring in the circumferential direction areprovided on the inner peripheral surface on both sides of the abutmentportion.
 7. The sealing device according to claim 4, wherein a convexportion which extends in the circumferential direction is provided at acenter in a width direction on the outer peripheral surface of the sealring, and a portion closer to the high pressure side than the convexportion is the concave portion.
 8. The sealing device according to claim2, wherein a guide portion which positions the metal spring in an axialdirection is formed on the inner peripheral surface of the seal ring. 9.The sealing device according to claim 5, wherein a convex portion whichextends in the circumferential direction is provided at a center in awidth direction on the outer peripheral surface of the seal ring, and aportion closer to the high pressure side than the convex portion is theconcave portion.
 10. The sealing device according to claim 6, wherein aconvex portion which extends in the circumferential direction isprovided at a center in a width direction on the outer peripheralsurface of the seal ring, and a portion closer to the high pressure sidethan the convex portion is the concave portion.